This invention relates to a small-capacity coffee roaster suitable for roasting relatively small amounts of raw coffee beans. This small-capacity coffee roaster can be used in the home or at a coffee shop, etc., to roast only the amount of raw coffee beans needed to brew the desired amount of coffee, and it is also capable of being built into a fully automatic coffee maker which performs all of the processes from the roasting of the raw coffee beans to the brewing of the coffee.
In the past, the roasting of raw coffee beans has been generally carried out by commercial operations which roast large quantities of beans using large bulk roasters. The end user would then purchase the preroasted coffee beans (either whole roasted beans or preground beans) and brew coffee from them. In other words, in the past, roasters were generally not available for the roasting of coffee beans in small quantities by the end user in order to provide only the amount needed for the amount of brewed coffee desired. In response to this situation, the present applicant proposed fully automatic coffee makers capable of providing brewed coffee from raw coffee beans, as described in Japanese patent early publication Hei. 2-237,519 dated Sept. 20 1990, early publication Hei. 3-251,212 dated Nov. 8 1991, and early publication Hei. 4-40916 dated Feb. 12 1992. These coffee makers are equipped with a small-capacity coffee roaster for roasting only the required quantity of raw coffee beans. While this small-capacity coffee roaster is a direct-contact heating type, in other fully automatic coffee makers, such as those proposed in Japanese Patent Publication Hei. 3-16128, Japanese Patent Early Publications Hei. 1-190317 and Hei. 1-190318, and Japanese Patent Publication Sho. 35-18243, the roaster is of a hot-air type.
However, even when the capacity of the bulk coffee roasters of the prior art, which used iron or stainless steel roasting drums, was reduced in size for small-capacity roasting, it was not possible to roast small quantities of coffee beans in such a way that they would provide delicious brewed coffee. With the direct-contact heating type roasters of the prior art in particular, there was the problem that it was not possible to control the temperature with sufficient accuracy to properly roast the coffee beans in small quantities, and the beans would become burned before they had been properly roasted, that is, before they had expanded sufficiently and become sufficiently porous.
Thus, the primary objective of this invention is to provide a small-capacity coffee roaster which solves the problems of the prior art described above, wherein even when roasting small quantities of raw coffee beans using direct-contact heat, the temperature can easily be controlled within the range vital for the roasting of raw coffee beans, and proper roasting can be accomplished in a short time.